Even the best climate models are affected by uncertainty in how much aerosols contribute to global warming. That uncertainty could mean that emissions cuts could reduce warming -- or that it might continue to increase for a while, despite cuts. Those are the conclusions of a recent review published by a University of Washington grad student. (Source: NOAA)

Researcher calls the conclusions of the UN's IPCC incomplete and flawed

Kyle
Armour, a doctoral student in physics at the University of Washington is boldly
challenging that certain assertions of the Nobel Prize-winning International Panel on
Climate Change, in their current state, may be flawed. He argues that the UN's suggestion that stopping aerosol
emissions will stop warming is misleading [press release]. These conclusions are
noteworthy, given the controversial state of warming research and
legislation aimed to "stop" global warming.

At issue is various climatology models, collected from published
research, that attempt to simulate the effects of changing global climate
variables. These variables include changing the levels of an "aerosols"
(atmospheric dust) like sea salt or soot from burning fossil fuels; or
greenhouse gases (GHGs) like CO2 or methane. The effects
of these variables are dubbed "forcings" (aerosol forcing, GHG
forcings, solar forcing, etc.). Various forcings sum up to predict a net
climate change and its contributors by approximate percentage.

Models are typically fit to current data, but the narrow range that many
climate variables have been constrained to in the modern era limits them.
They're also limited by how many variables and effects on those variables they
consider. Last, but not least, they're limited by how accurately and
completely we can measure certain variables (e.g. total global aerosol levels).

In this case, Kyle Armour says that current models are flawed in that they fail
to consider how high the uncertainty is regarding the amount that aerosols
contribute to climate change.

He says that the aerosols could contribute a lot to climate change, or only a
little.

In the "best case" scenario they would only contribute a little to net
warming, thus they would not be masking the effects of GHG-related warming. If all emissions of aerosols and GHGs stopped (a cessation of
fossil fuel burning, and mammalian
livestock farming, in short) the aerosols would quickly exit the
atmosphere. GHGs would remain for years at elevated levels, but the net
result would be a slight decrease in temperatures by about half a degree
Fahrenheit, given that the aerosols were the chief culprits.

In other words, the current temperature, which is about 1.5 degrees Fahrenheit
above pre-Industrial Revolution levels would dip to only 1.0 degrees Fahrenheit
above that base level -- but wouldn’t return entirely for many years.

Society can obviously not just instantly cut emissions, Mr. Armour
acknowledges, but he says that such a scenario would offer justification to
emissions cuts.

However, it's also possible that aerosols offer a larger contribution and are masking the effects of GHGs. In this case,
even if emissions stopped, temperatures would continue to rise and likely reach
3.5 degrees Fahrenheit above pre-Industrial Revolution levels, as the GHGs
would persist in the atmosphere. Such a temperature increase would likely
cause some of the more severe predicted climate change effects (though it could
offer benefits
as well).

In other words, Mr. Armour is arguing that uncertainty in the aerosol components of models may lead to the IPCC significantly underestimating the amount of warming that will occur under various scenarios.

Mr. Armour says that keeping this uncertainty in mind is critical and the IPCC
needs to do a better job in doing so in its next report. He states,
"This is not an argument to say we should keep emitting aerosols. It is an
argument that we should be smart in how we stop emitting. And it's a call to
action because we know the warming we are committed to from what we have
emitted already and the longer we keep emitting the worse it gets."

One interesting conclusion of the study not explored by Mr. Armour is the
question of maximum forcing. Clearly historically temperatures rose due to
increased GHGs, but leveled off (reach equilibrium) or reversed as the global system dampened the warming
effects. (In other words the Earth remained habitable, if a bit hotter,
and didn't become some sort of arid, barren
fireball.) This equilibrium may be reached by a number of mechanisms -- radiative heat loss into space/changes in ocean currents/changes in atmospheric water vapor, etc. The question is what is the "maximum" reachable temperature?

If Mr. Armour is correct and we may already be locked in to a large temperature
rise, the question is whether we'll reach this maximum. If so, the
climate change will already be enacted. While this will be unfortunate in
some ways (population would have to shift, growing areas would shift, etc.) and
fortunate in others, humanity would already be forced to adapt to the change.

If indeed a maximum with dampening is destined to be reached, stopping
emissions would do little good (unless we can somehow remove a significant
quantity of GHGs from the atmosphere, which does not seem currently feasible).
Thus the question of whether fossil fuel and farming emissions should be
cut, and if so how much, largely rests on a data set that is largely unknown
and uncertain. Mr. Armour's key conclusion is in noting this, and in
noting that the IPCC needs to do a better job informing policy
makers (politicians) of this uncertainty.

Mr. Armour's work has been published [abstract]
in the journal Geophysical Research Letters.

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meh, I think the planet has heated & cooled istelf in cycles, regardless of what we humans do, & unless the planet is about to burn up in my lifetime, not really worried about it, but many folks make a lot of money spooking people & many people, especially religious folks will believe anything like worshipping an invisible man, where there is no proof one exists other than books saying he does. I think for the most part there is little we can do to reduce how the planet will heat or cool itself in that will make any difference in the near future.

quote: but many folks make a lot of money spooking people & many people, especially religious folks will believe anything like worshipping an invisible man, where there is no proof one exists other than books saying he does.

I don't understand what you mean. The problem isn't the religious folk, its the folks that don't believe in him, and especially the leaders of the nations who God put in control who don't recognise him. Either God is control of the weather or he isn't. If he doesn't exist, then obviously prayers to him won't make any difference.If he does exist, then we don't need to worry if we are good because he will keep it just right; but if we are bad e.g. pretending to believe he doesn't exist and then running around changing all the historical temperatures to pretend to show how badly he looked after us in the past and then saying he is going to do a bad job of looking after us in the future unless we make life more expensive for the poor people of this world, then we can expect him to get angry and give us temperatures that will make it obvious he is annoyed e.g. making temperatures considerably colder in America and Europe where the rich folk are than he would otherwise have done.The stupid part then is how cold does he have to make it before people will cry out to him in desperation?See, the problem isn't the religious folk, who would have responded to his anger quickly, but the "non-religious folk" who are too proud to respond.

Great points, if there is a God, & he is like the believers say then there is nothing we can do. He controls everything, the weather, the oceans, what will happen to us & this planet is going to happen regardless. Personally, I don't think prayers do anything, other than give humans some false sense like there some spirit protecting us. I think everything that happens happens because it's supposed to happen, whether you say 1000 prayers or no prayers, but as far as the planet heating & cooling, although, I try to do my part by limiting my footprint, I seriously doubt there is much we can do to change global warming that will make any difference in the near future, but that doesn't mean we shouldn't try. I am not bashing those who believe, I respect religious beliefs, I just don't have any, as I feel the good & the bad that is supposed to happen to me in my life is going to happen to me, whether I say a prayer or not. If I offended anyone please forgive me. My parentes raised me to be a productive, college educated, contributing member of society, & that's all the prayers I need.

1: No one disagrees there is a natrual cycle at work. Many factors, right down to plate tectonics can play a role in global temperatures due to changes in weather patterns [which themselves are only understood in the planets current configuration]. That does NOT preclude outside factors from interacting. EG: Its currently hypothesised most of the O2 in the atmosphere was created by algea and other primitive plant life, which had a significant effect on the atmosphere over time. How is 100 years of dumping billions of tons of CO2 into the atmosphere any different then early plant life dumping just as much O2 into the atmosphere? And I note, we went from 0% O2 concentration to over 20%...

2: Climate change would likely happen at an accelerated pace over time, due to various factors:a: White reflects, black absorbs. Less sea ice reflects less heat into the atmosphere, warming the planet farther. [The "albedo" effect if you will]b: CO2 traps more heat then it blocks out [causing an increase in temperature over time, even if levels stabalize]

3: No one is really sure what the exact results of climate change are. At least a few modles predicted a la nina effect in the US [which, coincidentally, we are currently in the middle of], which could have a localized cooling effect. Likewise, no one really has a clue what weather patterns would be like for any specific change, due to all the factors involved. Its even theoretically possible that a warming effect on the planet could change weather in such a way as to cause a not cooling effect; no one really knows.

4: Climite models have two limitations: Precision and speed. First, weather patterns can turn out completely differently by chaning a staring variable by as little as the 20th decimal point, which is beyond our capacity to measure. Secondly, if we inputted ALL the data we knew, you would never be able to actually compute the results due to speed limitations. These two reasons are why even short-term weather forcasts are near impossible to model with any degree of accuracy [Hurricanes and other storms being the primary examples of this behavior].

Its almost certain we are directly contributing to the current warming trend; to what degree is open for some debate.

And before someone points out all the snow we've been having, I do note that warmer temperatures lead to the air holding more precipitation...

Studies have recently shown that the amount of sea ice is not so important. Yes, more heat is absorbed in the summer due to ice not reflecting it out, but also during winter there is less ice to prevent the heat from being released again. www.wattsupwiththat.com posted an excerpt from the following paper:

"Its almost certain we are directly contributing to the current warming trend; to what degree is open for some debate."

This may be hard to argue against (as there is no measureable hypothesis to test), but raises some questions:

How much of our precious resources should we spend trying to eliminate the "human footprint" on the earth?

Why is this footprint something that should be eliminated? Don't all species of life on earth have some impact on it?

If we can't determine how much humans may be contributing, how would we be able to determine any sort of cost/benefit for any actions we may think about taking? Should humanity return to starvation and subsistence farming or hunting/gathering even if this prevents an immeasureable impact like 0.0001C temperature rise?

Do you think that some warming and/or CO2 increase is dominated by negative impacts to the earth, or humans, or other life on earth? We would likely have increased crop yields, requiring less land to support the same population, along with other benefits. Global cooling or the next ice age is what humanity should be more worried about.

Why is this a more worrisome problem than others that humans face, like world hunger, diseases, asteroid or comet impacts, etc? Especially since we know that there are large populations of hungry people around the world, but we have little certainty about our impact on climate and our ability to control it.

I don't see any reason to hand over money, freedom, and liberty to beauracracies in order to combat a problem that can't even be supported by any data other than the output of models designed to show that there will be devastating warming caused by humans. If carbon is the bogeyman, government control of your every activity or inactivity can be justified. If you protest, then you must be some planet-hating right wingnut (and possibly a racist as well).